NeoRules

Ok...
I have an 84 944 with unknown miles...
If I apply power to fuse number 2 in the Aux fuse panel the pump runs (but the car still won't start)

I purchased the car with the owner saying it needed a fuel pump.
I replaced the DME relay with a brand spanking new one and still no voltage on the #2 fuse in the Aux panel.

When I did jump the fuse so the pump ran the car still didn't start and the only time the tachometer moves is when the key is turned on and then off. (it will bounce)...

Since I replaced the relay is there another test point to check before looking for another DME?

When I turn the key everything pops on and works except no voltage to fuel pump... Perhaps it is the ignition switch.
Just looking for ideas before I through good money after bad...
Thanks JC

vro944om

pressure regulator?

NeoRules

I don't think so...
From what I understand the pressure regulator won't keep the electrical part from
working...
I have no voltage on fuse #2 of the auxiliary fuse box. This fuse won't get any power until the DME relay energizes.

Once the ignition key is turned on the relay should click and the pump runs.
I will try to put in a jumper from 30 to 87a and 87B on the relay itself (since I have two) to see if maybe the ignition isn't sending power to energize the relay in the first place.... It is very tight up under the dash so I have a hard time getting a meter up to the relay block....

jpk

Fuel pump doesn't run untill the DME sees a engine speed signal. Same sensor drives the tach. If you don't see the tach "bouncing " or reading a steady speed (like 400 rpm) while cranking, that's the first place to look.
Engine speed and refrence sensors are on the top of the belhousing - you can see them when you look down at the back of the engine. You can do a basic test of the sensor by checking the resistance. clarks-garage.com has the details.

Spidey944

AFAIK, the speed/ref sensors will kill injector pulse, but not pump opperation. Fuel pump will recieve power from the ignition switch when in crank/run postitions only. If you have tried the DME relay, and fuse #2 is not recieving any power, I would pull the fuse panel and check for connections at the panel itself, or breaks in the wiring. You may also be looking at an ignition switch issue.

NeoRules

Thanks spidey!... I put in the jumper bypass to get both the DME and the fuel pump power...
the fuel pump runs but no start..... The tack doesn't bounce....

Doesn't the DME have a pump ground going to that relay? I am beginning to worry that maybe the DME is dead...
Tomorrow I will turn the key on and check the ignition circuit to the fuse panel.... If that checks ok then it must be the DME right?
Could the DME prevent a perfectly good relay with proper signal from the ignition switch from working?

Thanks A ton for your help!!!!!
JC

NeoRules

Thanks JPK... I will try to test the speed and reference sensors tomorrow after I see if the ignition is sending signal....
Hmmmmmmmmmmmm
This is getting interesting...
JC

2BWise

JPK is correct. If the tach isn't bouncing then the reference sensor is faulty. It will not allow the DME to fire the injectors. If you are getting the pump to run by jumpering the relay then it should be good. Its quick and easy to check the resistance on the sensor, 30 sec max.

NeoRules

Just curious will late model computers run early cars?
Same with the reference sensors... I have two other cars that need motors etc. that I could borrow parts from if the sensors test bad...
Thanks JC

2BWise

As I understand it the sensors are the same.

For the DME - early DMEs need the early AFM and late DMEs with late AFMS.

NeoRules

ohhh yeah... thats right... late afm run different voltages...
Cool... Thanks.. JC

NeoRules

Well... I feel stupid...
Purchased the car for a lower price since the fuel pump was bad....
NOPE.... The battery was so weak that I only got 10-15 seconds of cranking even when jumped....
So I bought a new battery.....
cranked on it for about 45 seconds and then again for 30 seconds... she started and made all kinds of racket....
after about 5 mins she quieted down and I took her for a spin.....

the only real problem is the ignition switch and the grounds....
just inserting the key turns the accessories on including the radio...

But not a bad buy for what I had to put in it.....
JC

jpk

For the early cars, the radio relay gets power once the key is inserted. I didn't fully trace that circuit, but the seatbelt warning realy also gets power. Since that relay is shown as a closed block, I can't tell if it's just the chime or if the light sould come on as well.
Once you turn the key to the first position, pretty much everything else is powered up, windows, sunroof, HVAC, etc...